Wide angle lens module and vehicle vision system

ABSTRACT

A wide angle lens module includes a first lens and a second lens with negative refracting power, a third lens and a fourth lens with positive refracting power, a fifth lens with negative refracting power, a sixth lens with positive refracting power, and a seventh lens with negative refracting power. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are assembled in order from an object side to an image side.

CROSS REFERENCE

This application is a divisional application of patent application Ser.No. 12/061,888 filed on Apr. 3, 2008 from which it claims the benefit ofpriority under 35 U.S.C. 120. The patent application Ser. No. 12/061,888in turn claims the benefit of priority under 35 USC 119 from ChinesePatent Application 200710201428.2, filed on Aug. 22, 2007.

BACKGROUND

1. Technical Field

The present disclosure generally relates to lens modules and vehicles,and more particularly, to a wide angle lens module and a vehicle visionsystem having the wide angle lens module.

2. Description of Related Art

It is known that vehicles such as cars and trucks have blind spots evenwhen an operator uses rear view mirrors. Therefore, a camera-based rearview vision system has been proposed to eliminate the blind spots.

Typically, the camera-based rear view vision system includes a cameralocated on the rear of the vehicle. However, the field of vision of thetypical camera used in the vision systems is narrow and may still leaveblind spots.

Therefore, what is desired is to provide a camera with a wide angle lensmodule and a vehicle vision system having the wide angle lens module forproviding viewing angles that eliminate blind spots around the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vehicle having a wide angle lens module according to anexemplary embodiment.

FIG. 2 is a block diagram of the vehicle as illustrated in FIG. 1.

FIG. 3 is a block diagram of the wide angle lens module as illustratedin FIG. 1.

FIGS. 4A-4C respectively illustrates longitudinal spherical aberration,astigmatism, and distortion of a first exemplary embodiment.

FIGS. 5A-5C respectively illustrates longitudinal spherical aberration,astigmatism, and distortion of a second exemplary embodiment

FIGS. 6A-6C respectively illustrates longitudinal spherical aberration,astigmatism, and distortion of a third exemplary embodiment.

DETAILED DESCRIPTION

Embodiments of the disclosure will now be described in detail, withreference to the accompanying drawings.

Referring to FIGS. 1 and 2, a wide angle lens module 10 may be rigidlymounted to a rear panel of a vehicle 100 and directed substantially tothe rear of the vehicle 100. The vehicle 100 includes an image sensor 20such as a charge coupled device (CCD), a controller 30, a display unit40 such as a liquid crystal display (LCD), and a storage unit 50 such asa hard disk drive (HDD).

The wide angle lens module 10 is used for receiving light beams emittedby or reflected from outside objects existing in a wide viewing anglethat can be greater than 140°. The light beams received by the wideangle lens module 10 are directed to the image sensor 20. The imagesensor 20 converts the light beams received from the wide angle lensmodule 10 to electrical signals, which are digitized to form digitalimages. The digital images are displayed on the display unit 40. Thedigital images may also be encoded to image files, which are stored inthe storage unit 50. The controller 30 is a processing unit forcontrolling various operations of the vehicle 100.

Referring to FIG. 3, the wide angle lens module 10 includes a first lensgroup 12 and a second lens group 14. The first lens group 12 and thesecond lens group 14 are disposed in an order from an object side 16 toan image side 18. The wide angle lens module 10 is designed to be afixed-focal type wide angle lens module, such that a distance betweenthe first lens group 12 and the second lens group 14 is not adjustable.

The first lens group 12 has positive refracting power for effectivelyreceiving incident light beams at wide angles. Preferably, the firstlens group 12 satisfies the following condition: 0.8<f12/f<1.2 (1),wherein f is a system focal length of the wide angle lens module 10, andf12 is an effective focal length of the first lens group 12. Thecondition (1) is for configuring the wide angle lens module 10 tocorrect spherical aberrations. If the ratio f12/f is below the lowerlimit 0.8, astigmatism becomes great and high-order sphericalaberrations are difficult to correct. If the ratio f12/f is above theupper limit 1.2, the wide angle lens module 10 will not be compact.

The second lens group 14 also has positive refracting power forconverging light beams transmitted from the first lens group 12 to theimage sensor 20. Preferably, the second lens group 14 satisfies thefollowing condition: 5<f14/f<25 (2), wherein f14 is an effective focallength of the second lens group 14. The condition (2) is for designingthe wide angle lens module 10 to be similar to a telecentric opticalsystem, such that the light beams transmitted from the first lens group12 may be more effectively converged to the image sensor 20. If theratio f14/f is below the lower limit 5, coma aberrations become greatand lateral chromatic aberration is difficult to correct. If the ratiof14/f is above the upper limit 25, distortion becomes so great that itmay be difficult to correct. The condition (2) is also used for limitingthe second lens group 14 having relatively stronger refracting power inorder to make an overall length of the wide angle lens module 10 to beshorter.

The first lens group 12 includes a first lens 122, a second lens 124, athird lens 126, and a fourth lens 128 that are assembled in that orderfrom the object side 16 to the image side 18. The first lens 122 and thesecond lens 124 are both meniscus lenses having negative refractivepowers. Convex surfaces of the first lens 122 and the second lens 124face toward the object side 16. The third lens 126 and the fourth lens128 are both bi-convex lenses having positive refractive powers.

The second lens group 14 includes a fifth lens 144, a sixth lens 146,and a seventh lens 148. The fifth lens 144 is a bi-concave lens havingnegative refracting power. The sixth lens 146 is a bi-convex lens havingpositive refracting power. The seventh lens 148 is a meniscus lenshaving negative refracting power. A convex surface of the seventh lens148 faces toward the image side 18.

The first lens 122 satisfies the following condition: −5.5<f1/f<−4.5(3), wherein f1 is a focal length of the first lens 122. The condition(3) is for configuring the first lens 122 to receive light beamsincident at wide angles. If the ratio f1/f is below the lower limit−5.5, the wide angle lens module 10 will not be compact. If the ratiof1/f is above the upper limit −4.5, it will be difficult to manufacturethe first lens 122, particularly when the material is glass, because thefirst lens 122 has a relatively small radius of curvature in thiscondition.

The third lens 126 satisfies the following conditions: ν3<35 (4) and3.3<f3/f<3.6 (5), wherein ν3 is an Abbe number of the third lens 126 atd-line, and f3 is a focal length of the third lens 126. The condition(4) is for configuring the wide angle lens module 10 to correct thesystem chromatic aberration. The condition (5) is for configuring thewide angle lens module 10 to correct the distortion. If the ratio f3/fis below the lower limit 3.3, it is difficult to manufacture the thirdlens 122. If the ratio f3/f is above the upper limit 3.6, the third lens126 may not be able to provide sufficient positive refracting power andit may be difficult to correct the spherical aberration and distortion.

The sixth lens 146 satisfies the following condition: 1<f6/f<1.2 (6),wherein f6 is a focal length of the sixth length 146. The condition isfor configuring the wide angle lens module 10 to correct astigmatism. Ifthe ratio f6/f is below the lower limit 1, it is difficult tomanufacture the sixth lens 146. If the ratio f6/f is above the upperlimit 1.2, it is difficult to correct the astigmatism.

Preferably, the wide angle lens module 10 may further include anaperture stop 13. The aperture stop 13 is positioned between the fourthlens 128 of the first lens group 12 and the fifth lens 144 of the secondlens group 14. The aperture stop 13 is used for providing an opening forrestricting the amount of light beams transmitted from the first lensgroup 12 to the second lens group 14. That is, if the aperture stop 13has a wider opening, the image brightness and definition may beincreased, while the depth of field and contrast of the image arecorrespondingly decreased. The aperture stop 13 may be positionedbetween lens elements in the first lens group 12 or between lenselements in the second lens group 14 according to specific applications.

In order to control an overall length of the wide angle lens module 10,the wide angle lens module 10 preferably satisfies the followingcondition: 0.1<f/TTL<0.13 (7), wherein TTL is an overall length of thewide angle lens module 10. If the ratio f/TTL is below the lower limit0.1, it is difficult to correct high-order spherical aberrations. If theratio f/TTL is above the upper limit 0.13, it is difficult toeffectively shorten the overall length of the wide angle lens 10.

Preferably, the first lens 122, the second lens 124, the third lens 126,the fourth lens 128, the fifth lens 144, the sixth lens 146, and theseventh lens 148 are made of glass material. The glass material lens ismore resistant to high temperature, erosion, scratches etcetera.Opposite convex and/or concave surfaces of the first lens 122, thesecond lens 124, the third lens 126, the fourth lens 128, the fifth lens144, the sixth lens 146, and the seventh lens 148 are spherical, becausemanufacturing spherical surfaces is more cost effective thanmanufacturing aspherical surfaces.

The following are symbols used in the exemplary embodiment.

r: radius of curvature

d: distance between adjacent two surfaces along optical axis of the wideangle lens module 10

n: refractive index of the lens at d-line

ν: Abbe number of the lens at d-line

EXAMPLE 1

Table 1 shows lens data of the wide angle lens module 10 of a firstexemplary embodiment.

TABLE 1 f12/f = 0.8463 f14/f = 21.5039 f1/f = −5.1 f3/f = 3.5 f6/f = 1.1f/TTL = 0.127 Surface r(mm) d(mm) n ν  1st 11.087 0.700 1.743972 44.8504 2nd 4.129 1.612  3rd 17.004 0.700 1.730126 45.9733  4th 2.908 1.169 5th 12.423 5.000 1.755201 27.5795  6th −6.450 0.100  7th 2.539 1.0491.62041 60.3236  8th −17.265 0.100 stop infinite 0.100  9th −10.5290.792 1.74402 28.0464 10th 2.965 0.100 11th 4.717 1.226 1.743972 44.850412th −2.007 0.252 13th −1.518 0.700 1.755201 27.5795 14th −3.036 1.600

Referring to FIGS. 4A-4C, longitudinal spherical aberrations,astigmatism (field curvature), and distortion are respectivelyillustrated for the first embodiment of the wide angle lens module 10having lens data listed in table 1, where half of the field angle (ω) ofthe first embodiment can be as much as 71.57°.

EXAMPLE 2

Table 2 shows lens data of the wide angle lens module 10 of a secondexemplary embodiment.

TABLE 2 f12/f = 0.9381 f14/f = 8.5851 f1/f = −5.49 f3/f = 3.5 f6/f = 1.1f/TTL = 0.122 Surface r(mm) d(mm) n ν  1st 9.814 0.700 1.786097 44.2503 2nd 4.189 1.716  3rd 22.296 0.700 1.716367 47.1926  4th 2.896 1.585 5th 9.577 4.000 1.785201 26.5795  6th −8.126 0.154  7th 2.711 0.9901.62041 60.3236  8th −13.841 0.120 Stop infinite 0.120  9th −10.5230.700 1.726093 28.861 10th 3.244 0.120 11th 5.400 1.199 1.786097 44.250312th −2.010 0.243 13th −1.542 0.700 1.755201 27.5795 14th −3.084 1.620

Referring to FIGS. 5A-5C, longitudinal spherical aberrations,astigmatism (field curvature), and distortion are respectivelyillustrated of a second example of the wide angle lens module 10 havinglens data listed in table 2, where half of the field angle (ω) can be asmuch as 72.24°.

EXAMPLE 3

Table 3 shows lens data of the wide angle lens module 10 of a thirdexemplary embodiment.

TABLE 3 f12/f = 1.0353 f14/f = 5.5722 f1/f = −4.91 f3/f = 3.5 f6/f = 1.1f/TTL = 0.127 Surface r(mm) d(mm) n ν  1st 10.721 0.710 1.803972 42.8504 2nd 4.164 1.657  3rd 18.712 0.710 1.703779 48.4112  4th 2.950 1.310 5th 11.214 3.800 1.805201 25.5795  6th −8.135 0.140  7th 2.849 1.1391.62041 60.3236  8th −13.227 0.110 Stop infinite 0.110  9th −14.7730.710 1.714641 29.4296 10th 3.144 0.105 11th 5.614 1.249 1.80397242.8504 12th −1.915 0.223 13th −1.558 0.710 1.785201 26.3795 14th −3.1171.610

Referring to FIGS. 6A-6C, longitudinal spherical aberrations,astigmatism (field curvature), and distortion are respectivelyillustrated of a third example of the wide angle lens module 10 havinglens data listed in table 2 where half of the field angle (ω) can be asmuch as 70.91°.

It will be understood that particular embodiments and methods are shownand described by way of illustration only. The principles and thefeatures of the present disclosure may be employed in various andnumerous embodiments thereof without departing from the scope of thedisclosure as claimed. The above-described embodiments illustrate thescope of the disclosure but do not restrict the scope of the disclosure.

1. A wide angle lens module comprising: a first lens group with positiverefracting power; and a second lens group with positive refractingpower, the first lens group and the second lens group being disposed inorder from an object side to an image side, the first lens group and thesecond lens group satisfying the following conditions: 0.8<f12/f<1.2(1), 5<f14/f<25 (2), wherein f12 is an effective focal length of thefirst lens group, f14 is an effective focal length of the second lensgroup, and f is a focal length of the wide angle lens module.
 2. Thewide angle lens module as described in claim 1, wherein the first lensgroup comprises: a first lens with negative refracting power; a secondlens with negative refracting power; a third lens with positiverefracting power, the first lens and the third lens satisfying thefollowing conditions: −5.5<f1/f<−4.5 (3), 3.3<f3/f<3.6 (4), ν3<35 (5),wherein f1 is a focal length of the first lens, f3 is a focal length ofthe third lens, ν3 is an Abbe number of the third lens; and a fourthlens with positive refracting power.
 3. The wide angle lens module asdescribed in claim 2, wherein the first lens is a meniscus lens having aconvex surface facing toward the object side.
 4. The wide angle lensmodule as described in claim 2, wherein the second lens is disposedbetween the first lens and the third lens, the second lens is a meniscuslens having a convex surface facing toward the object side.
 5. The wideangle lens module as described in claim 2, wherein the third lens andthe fourth lens are bi-convex lenses.
 6. The wide angle lens module asdescribed in claim 1, wherein the second lens group comprises: a fifthlens with negative refracting power; a sixth lens with positiverefracting power, the sixth lens satisfying the following condition:1<f6/f<1.2 (6), wherein f6 is a focal length of the sixth lens; and aseventh lens with negative refracting power.
 7. The wide angle lensmodule as described in claim 6, wherein the fifth lens is a bi-concavelens and the sixth lens is a bi-convex lens, the sixth lens is disposedbetween the fifth lens and the seventh lens.
 8. The wide angle lensmodule as described in claim 6, wherein the seventh lens is a meniscuslens having a convex surface facing toward the image side.
 9. The wideangle lens module as described in claim 1, wherein the wide angle lensmodule further satisfies the following condition: 0.1<f/TTL<0.13,wherein TTL is an overall length of the wide angle lens module.
 10. Thewide angle lens module as described in claim 1, wherein the wide anglelens module further satisfies the following condition: 2ω>140°, whereinω is a half field angle of the wide angle lens module.
 11. The wideangle lens module as described in claim 1, wherein the wide angle lensmodule further comprises: an aperture stop, the aperture stop isdisposed between the first lens group and the second lens group.
 12. Theflash module as claimed in claim 1, wherein the lens data of the wideangle lens module is: 0.8<f12/f≦1.0353.
 13. The flash module as claimedin claim 12, wherein the lens data of the wide angle lens module is:0.8463≦f12/f≦0.9381.
 14. A vehicle vision system configured forcapturing images around a vehicle, the vehicle vision system comprising:a wide angle lens module mounted to a portion of the vehicle forreceiving light beams originated from objects around the vehicle, thewide angle lens module comprising: a first lens group with positiverefracting power; and a second lens group with positive refractingpower, the first lens group and the second lens group being disposed inorder from an object side to an image side, the first lens group and thesecond lens group satisfying the following conditions: 0.8<f12/f<1.2(1), 5<f14/f<25 (2), wherein f12 is an effective focal length of thefirst lens group, f14 is an effective focal length of the second lensgroup, and f is a focal length of the wide angle lens module; an imagesensor for receiving light beams transmitted from the wide angle lensmodule and generating digital images; a display unit for displaying thedigital images.
 15. The vehicle vision system as described in claim 14,wherein the first lens group comprises: a first lens with negativerefracting power; a second lens with negative refracting power; a thirdlens with positive refracting power, the first lens and the third lenssatisfying the following conditions: −5.5<f1/f<−4.5 (3), 3.3<f3/f<3.6(4), ν3<35 (5), wherein f1 is a focal length of the first lens, f3 is afocal length of the third lens, ν3 is an Abbe number of the third lens;and a fourth lens with positive refracting power.
 16. The vehicle visionsystem as described in claim 14, wherein the second lens groupcomprises: a fifth lens with negative refracting power; a sixth lenswith positive refracting power, the sixth lens satisfying the followingcondition: 1<f6/f<1.2 (6), wherein f6 is a focal length of the sixthlens; and a seventh lens with negative refracting power.
 17. The vehiclevision system as described in claim 14, wherein the wide angle lensmodule further satisfies the following condition: 0.1<f/TTL<0.13 (7),wherein TTL is an overall length of the wide angle lens module.
 18. Thevehicle vision system as described in claim 14, wherein the wide anglelens module further satisfies the following condition: 2ω>140° (8),wherein ω is a half field angle of the wide angle lens module.
 19. Thevehicle vision system as described in claim 14, wherein the lens data ofthe wide angle lens module is: 0.8<f12/f≦1.0353.
 20. The vehicle visionsystem as described in claim 19, wherein the lens data of the wide anglelens module is: 0.8463≦f12/f≦0.9381.